Does 3pi/5 have a supplementary angle?

If two angles are supplementary, then their measures add to 180 deg.

Since 180 deg = pi rad, then supplementary angles are two angles whose measures add to pi rad.

Since 3pi/5 is less than 1 rad, then there is an angle that is supplementary to an angle measuring 3pi/5. The measure of the supplement is 2pi/5.